Geoderma, March, 2013, Vol.195-196, p.70(9)
To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.geoderma.2012.11.014 Byline: Roy Kasteel, Frauke Schnitzler, Anne E. Berns, Jan Vanderborght, Harry Vereecken Keywords: Vadose zone; Dye tracers; Contaminant transport; Preferential flow Abbreviations: MRZ, Merzenhausen; SCH, Scheyern; BaP, benzo[a]pyrene; BB, Brilliant Blue; TLC, thin layer chromatography Abstract: Small amounts of organic compounds are often found at much larger depths than expected from their organic carbon normalized distribution coefficient (K.sub.oc). In this study the food dye Brilliant Blue (BB) was used to visualize the (preferential) transport pathways in undisturbed soil monoliths taken from an Orthic Luvisol and from a Eutric Cambisol. After spiking the monoliths with 1.0MBq of either.sup.14C-labeled benazolin (leacher) or.sup.14C-labeled benzo[a]pyrene (BaP, nonleacher), they were intermittently irrigated under free-draining conditions twice weekly with 4mm of rain water for 17weeks. BB (4gL.sup.-1) was added to the rain water during the last 4weeks. After irrigation, the monoliths were sliced and photographs were taken from horizontal cross-sections. Soil was dried and incinerated to measure total.sup.14C-activity. The mean travel depth for benazolin (6-7cm) was larger than for BaP (2cm), which is in line with their K.sub.oc values, although BaP was much more mobile than expected from the K.sub.oc value. BB patterns, arbitrarily classified into five intensity classes, showed that large parts of the monolith were bypassed below the completely stained upper two to five centimeter. Furthermore, BB patterns indicated the locations of strongly sorbing compounds in the deeper soil layers and are therefore a helpful tool to selectively sample the soil for these compounds. A continuously stained root channel below the 20-cm depth contained substantial amounts of BaP, indicating that soil structure cannot be neglected to assess the fate of nonleachers in undisturbed soils. Article History: Received 3 July 2012; Revised 19 November 2012; Accepted 21 November 2012
Tracers (Chemistry) ; Soil Structure ; Recharge Zones ; Rainwater ; Vadose Zone
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